Method and apparatus for manufacturing press component

Abstract

A method and apparatus for manufacturing a press component without generating cracks in a flange on an inner circumferential side of a curved portion includes press working by a free bending method on a blank consisting of an ultra-high tensile strength steel sheet. A press component is manufactured by performing cold press working on a blank of an ultra-high tensile strength steel sheet. By the press working, a material inflow facilitating portion that increases the amount by which a portion of the blank to be formed into an end portion of the press component flows into a portion of the blank to be formed into a flange on an inner circumferential side of the curved portion of the press component is provided in the vicinity of the portion of the blank to be formed into the flange on an inner circumferential side of the curved portion of the press component.

The invention claimed is: 
     
       1. A method for manufacturing a press component, by performing press working on a blank or a pre-formed blank disposed between a die and a die pad, and a punch that is disposed facing the die and die pad,
 the press component having a top plate extending in a first direction, a convex ridge line connecting to an end portion of the top plate in a direction orthogonal to the first direction, a vertical wall connecting to the convex ridge line, a concave ridge line connecting to the vertical wall, and a flange connecting to the concave ridge line, and also having a curved portion at which the convex ridge line, the vertical wall and the concave ridge line are curved in a plan view that is orthogonal to the top plate, 
 the method comprising, when manufacturing the press component: 
 pressing a portion of the blank to be formed into a part of the top plate by the die pad with an applied pressure of 1.0 MPa or more and less than 32.0 MPa, or subjecting the die pad to approach or come in contact with a portion of the blank to be formed into a part of the top plate while maintaining a gap between the die pad and the punch at a distance that is not less than a sheet thickness of the blank and not more than 1.1 times the sheet thickness of the blank, and 
 forming the vertical wall, the concave ridge line and the flange by relatively moving the die and the punch in directions in which the die and the punch approach each other while causing a portion of the blank that is to be formed into an end portion of the top plate in the first direction to move in-plane over a portion of the die at which the top plate will be formed, 
 wherein, 
 by the press working, in a first portion of the blank to be formed into the flange on an inner circumferential side of the curved portion or a second portion of the blank that is outside the first portion, one or more material inflow facilitating portions are provided, the material inflow facilitating portions increasing an inflow amount of material flowing into the first portion, and 
 the material inflow facilitating portion is formed so as to protrude toward a same side as the top plate or protrude toward an opposite side to the top plate. 
 
     
     
       2. The method for manufacturing a press component according to  claim 1 , wherein the method satisfies at least one of the following conditions:
 the blank comprises an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more; 
 a projection distance of the vertical wall in a product height direction as a height of the press component is 70 mm or more; 
 a radius of curvature of the concave ridge line of the press component is 10 mm or less in side view; and 
 a radius of curvature on the inner circumferential side of the curved portion in the press component is 100 mm or less in the plan view. 
 
     
     
       3. The method for manufacturing a press component according to  claim 1 , wherein the method satisfies two or more of the following conditions:
 the blank comprises an ultra-high tensile strength steel sheet having a tensile strength of 1180 MPa or more; 
 a projection distance of the vertical wall in a product height direction as a height of the press component is 55 mm or more; 
 a radius of curvature of the concave ridge line of the press component is 15 mm or less in side view, and 
 a radius of curvature on an inner side of the curved portion in the press component is 140 mm or less in the plan view. 
 
     
     
       4. The method for manufacturing a press component according to  claim 1 , wherein:
 in the blank, the material inflow facilitating portion is provided at a region that is outside of a region to be formed into the press component. 
 
     
     
       5. The method for manufacturing a press component according to  claim 1 , wherein:
 the concave ridge line has a curved region that is included in the curved portion, and 
 a radius of curvature on an inner circumference of the curved region is 140 mm or less in the plan view, and further wherein 
 when a straight line that is tangent to a center position of the inner circumference of the curved region of the concave ridge line in the plan view is defined as a reference line, and a length of a line passing through a center of the material inflow facilitating portion in a cross-section that is parallel to the reference line in the plan view is defined as a cross-sectional line length, 
 the material inflow facilitating portion has a region in which the cross-sectional line length increases as a distance from the center position increases in the plan view. 
 
     
     
       6. The method for manufacturing a press component according to  claim 1 , wherein:
 the material inflow facilitating portion is a convex bead that is convex toward a same side as the top plate of the press component, or is a concave bead that is convex toward an opposite side to the top plate of the press component. 
 
     
     
       7. The method for manufacturing a press component according to  claim 1 , wherein:
 the material inflow facilitating portion is provided in a stepped shape in a direction parallel to a sheet thickness direction of the blank. 
 
     
     
       8. The method for manufacturing a press component according to  claim 5 , wherein:
 the material inflow facilitating portion has a region in which the cross-sectional line length is constant at positions having different distances from the center position in the plan view. 
 
     
     
       9. The method for manufacturing a press component according to  claim 1 , wherein:
 the press component has a hat-shaped cross-sectional shape. 
 
     
     
       10. An apparatus for manufacturing a press component by carrying out the method according to  claim 1 , the apparatus comprising a die and a die pad, and a punch that is disposed facing the die and die pad,
 wherein: 
 the die and the punch comprise a material inflow facilitating portion forming mechanism which includes a recess provided in the die and a protrusion provided in the punch or a recess provided in the punch and a protrusion provided in the die; and 
 the one or more material inflow facilitating portions by the material inflow facilitating forming mechanism. 
 
     
     
       11. The apparatus for manufacturing a press component according to  claim 10 , wherein:
 the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion at a region of the blank that is outside of a region to be formed into the press component. 
 
     
     
       12. An apparatus for manufacturing a press component by carrying out the method according to  claim 5 , the apparatus comprising a die and a die pad, and a punch that is disposed facing the die and die pad, wherein:
 the die and the punch comprise a material inflow facilitating portion forming mechanism which includes a recess provided in the die and a protrusion provided in the punch or a recess provided in the punch and a protrusion provided in the die; 
 the die and the punch provide the one or more material inflow facilitating portions by the material inflow facilitating portion forming mechanism; and 
 the material inflow facilitating portion forming mechanism forms the material inflow facilitating portion so as to have region in which the cross-sectional line length increases as a distance from the center position increases in the plan view. 
 
     
     
       13. The apparatus for manufacturing a press component according to  claim 10 , wherein:
 the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion, which is a convex bead that is convex toward a same side as the top plate of the press component, or is a concave bead that is convex toward an opposite side to the top plate of the press component. 
 
     
     
       14. The apparatus for manufacturing a press component according to  claim 10 , wherein:
 the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion in a stepped shape in a direction parallel to a sheet thickness direction of the blank. 
 
     
     
       15. The apparatus for manufacturing a press component according to  claim 12 , wherein:
 the material inflow facilitating portion forming mechanism provides the material inflow facilitating portion so as to have a region in which the cross-sectional line length is constant at positions having different distances from the center position in the plan view. 
 
     
     
       16. The apparatus for manufacturing a press component according to  claim 10 , wherein:
 the die, the die pad, and the punch are configured to form the press component, the press component having a hat-shaped cross-sectional shape.